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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only Exploring projection based mixed reality with tangibles for nonsymbolic preschool math education(Assoc Computing Machinery, 2019) N/A; N/A; Department of Psychology; Department of Media and Visual Arts; Department of Electrical and Electronics Engineering; Salman, Elif; Beşevli, Ceylan; Göksun, Tilbe; Özcan, Oğuzhan; Ürey, Hakan; Master Student; Researcher; Faculty Member; Faculty Member; Faculty Member; Department of Psychology; Department of Media and Visual Arts; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Graduate School of Social Sciences and Humanities; College of Social Sciences and Humanities; College of Social Sciences and Humanities; College of Engineering; N/A; N/A; 47278; 12532; 8579A child's early math development can stem from interactions with the physical world. Accordingly, current tangible interaction studies focus on preschool children's formal (symbolic) mathematics, i.e. number knowledge. However, recent developmental studies stress the importance of nonsymbolic number representation in math learning, i.e. understanding quantity relations without counting(more/less). To our knowledge, there are no tangible systems based on this math concept. We developed an initial tangible based mixed-reality(MR) setup with a small tabletop projector and depth camera. Our goal was observing children's interaction with the setup to guide our further design process towards developing nonsymbolic math trainings. In this paper we present our observations from sessions with four 3-to-5 year old children and discuss their meaning for future work. Initial clues show that our MR setup leads to exploratory and mindful interactions, which might be generalizable to other tangible MR systems for child education and could inspire interaction design studies.Publication Metadata only Coarse-to-fine surface reconstruction from silhouettes and range data using mesh deformation(Academic Press Inc Elsevier Science, 2010) N/A; Department of Computer Engineering; Sahillioğlu, Yusuf; Yemez, Yücel; PhD Student; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; 215195; 107907We present a coarse-to-fine surface reconstruction method based on mesh deformation to build watertight surface models of complex objects from their silhouettes and range data. The deformable mesh, which initially represents the object visual hull, is iteratively displaced towards the triangulated range surface using the line-of-sight information. Each iteration of the deformation algorithm involves smoothing and restructuring operations to regularize the surface evolution process. We define a non-shrinking and easy-to-compute smoothing operator that fairs the surface separately along its tangential and normal directions. The mesh restructuring operator, which is based on edge split, collapse and flip operations, enables the deformable mesh to adapt its shape to the object geometry without suffering from any geometrical distortions. By imposing appropriate minimum and maximum edge length constraints, the deformable mesh, hence the object surface, can be represented at increasing levels of detail. This coarse-to-fine strategy, that allows high resolution reconstructions even with deficient and irregularly sampled range data, not only provides robustness, but also significantly improves the computational efficiency of the deformation process. We demonstrate the performance of the proposed method on several real objects.Publication Metadata only Noninvasive in vivo determination of residual strains and stresses(ASME, 2015) N/A; Department of Molecular Biology and Genetics; Department of Mechanical Engineering; Donmazov, Samir; Pişkin, Şenol; Pekkan, Kerem; PhD Student; Researcher; Faculty Member; Department of Molecular Biology and Genetics; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; 148702; 161845Vascular growth and remodeling during embryonic development are associated with blood flow and pressure induced stress distribution, in which residual strains and stresses play a central role. Residual strains are typically measured by performing in vitro tests on the excised vascular tissue. In this paper, we investigated the possibility of estimating residual strains and stresses using physiological pressure-radius data obtained through in vivo noninvasive measurement techniques, such as optical coherence tomography or ultrasound modalities. This analytical approach first tested with in vitro results using experimental data sets for three different arteries such as rabbit carotid artery, rabbit thoracic artery, and human carotid artery based on Fung's pseudostrain energy function and Delfino's exponential strain energy function (SEF). We also examined residual strains and stresses in the human swine iliac artery using the in vivo experimental ultrasound data sets corresponding to the systolic-to-diastolic region only. This allowed computation of the in vivo residual stress information for loading and unloading states separately. Residual strain parameters as well as the material parameters were successfully computed with high accuracy, where the relative errors are introduced in the range of 0-7.5%. Corresponding residual stress distributions demonstrated global errors all in acceptable ranges. A slight discrepancy was observed in the computed reduced axial force. Results of computations performed based on in vivo experimental data obtained from loading and unloading states of the artery exhibited alterations in material properties and residual strain parameters as well. Emerging noninvasive measurement techniques combined with the present analytical approach can be used to estimate residual strains and stresses in vascular tissues as a precursor for growth estimates. This approach is also validated with a finite element model of a general two-layered artery, where the material remodeling states and residual strain generation are investigated.Publication Metadata only Threshold single password authentication(Springer International Publishing Ag, 2017) N/A; N/A; Department of Computer Engineering; İşler, Devriş; Küpçü, Alptekin; Master Student; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 168060Passwords are the most widely used form of online user authentication. In a traditional setup, the user, who has a human-memorable low entropy password, wants to authenticate with a login server. Unfortunately, existing solutions in this setting are either non-portable or insecure against many attacks, including phishing, man-in-the-middle, honeypot, and offline dictionary attacks. Three previous studies (Acar et al. 2013, Bicakci et al. 2011, and Jarecki et al. 2016) provide solutions secure against offline dictionary attacks by additionally employing a storage provider (either a cloud storage or a mobile device for portability). These works provide solutions where offline dictionary attacks are impossible as long as the adversary does not corrupt both the login server and the storage provider. For the first time, improving these previous works, we provide a more secure generalized solution employing multiple storage providers, where our solution is proven secure against offline dictionary attacks as long as the adversary does not corrupt the login server and threshold-many storage providers. We define ideal and real world indistinguishability for threshold single password authentication (Threshold SPA) schemes, and formally prove security of our solution via ideal-real simulation. Our solution provides security against all the above-mentioned attacks, including phishing, man-in-the-middle, honeypot, and offline dictionary attacks, and requires no change on the server side. Thus, our solution can immediately be deployed via a browser extension (or a mobile application) and support from some storage providers. We further argue that our protocol is efficient and scalable, and provide performance numbers where the user and storage load are only a few milliseconds.Publication Metadata only Novel nanostructured composites of silica aerogels with a metal organic framework(Elsevier, 2013) N/A; N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Ülker, Zeynep; Eruçar, İlknur; Keskin, Seda; Erkey, Can; PhD Student; PhD Student; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; 262388; 260094; 40548; 29633Novel nanostructured composites of silica aerogel with Cu-BTC were synthesized using a slightly modified version of the conventional sol-gel method used to synthesize silica aerogels. The composite materials had monolithic structures with blue color consisting of well dispersed microporous domains of Cu-BTC in the mesoporous inorganic silica aerogel network. The Cu-BTC content in the composites ranged from 5 to 30 weight percent and the total surface area of the composites ranged from 1025 to 1138 m(2)/g. The microporosity of the composites increased with the increasing amount of Cu-BTC indicating that the micropores of Cu-BTC were accessible and functional. XRD analysis indicated that Cu-BTC retained its crystal structure in the composite despite being immersed in a solution containing water, ethanol and tetraethylorthosilicate. Additionally, it was observed that increasing Cu-BTC content caused a decrease in the average desorption pore radius with a wider pore size distribution. Nitrogen adsorption isotherms for composites could be predicted using the experimentally obtained pure component isotherm for the silica aerogel, theoretically obtained isotherm for Cu-BTC and the weight fractions of the components within the composite material.Publication Metadata only Working memory capacity and controlled serial memory search(Elsevier, 2016) N/A; Department of Psychology; Mızrak, Eda; Öztekin, İlke; PhD Student; Faculty Member; Department of Psychology; Graduate School of Social Sciences and Humanities; College of Social Sciences and Humanities; N/A; N/AThe speed-accuracy trade-off (SAT) procedure was used to investigate the relationship between working memory capacity (WMC) and the dynamics of temporal order memory retrieval. High- and low-span participants (HSs, LSs) studied sequentially presented five-item lists, followed by two probes from the study list. Participants indicated the more recent probe. Overall, accuracy was higher for HSs compared to LSs. Crucially, in contrast to previous investigations that observed no impact of WMC on speed of access to item information in memory (e.g., Oztekin & McElree, 2010), recovery of temporal order memory was slower for LSs. While accessing an item's representation in memory can be direct, recovery of relational information such as temporal order information requires a more controlled serial memory search. Collectively, these data indicate that WMC effects are particularly prominent during high demands of cognitive control, such as serial search operations necessary to access temporal order information from memory. (C) 2016 Elsevier B.V. All rights reserved.Publication Metadata only FlexDPDP: flexlist-based optimized dynamic provable data possession(assoc Computing Machinery, 2016) N/A; N/A; N/A; Department of Computer Engineering; Department of Computer Engineering; Department of Computer Engineering; Esiner, Ertem; Kachkeev, Adilet; Küpçü, Alptekin; Özkasap, Öznur; Master Student; Master Student; N/A; Faculty Member; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; N/A; 168060; 113507With increasing popularity of cloud storage, efficiently proving the integrity of data stored on an untrusted server has become significant. authenticated skip lists and rank-based authenticated skip lists (RBaSL) have been used to provide support for provable data update operations in cloud storage. However, in a dynamic file scenario, An RBaSL based on block indices falls short when updates are not proportional to a fixed block size; such an update to the file, even if small, may result in O(n) updates on the data structure for a file with n blocks. To overcome this problem, we introduce FlexList, A flexible length-based authenticated skip list. FlexList translates variable-size updates to O(inverted right perpendicularu/Binverted left perpendicular) insertions, removals, or modifications, where u is the size of the update and B is the (average) block size. We further present various optimizations on the four types of skip lists (regular, Authenticated, rank-based authenticated, and FlexList). We build such a structure in O(n) time and parallelize this operation for the first time. We compute one single proof to answer multiple (non) membership queries and obtain efficiency gains of 35%, 35%, and 40% in terms of proof time, energy, and size, respectively. We propose a method of handling multiple updates at once, Achieving efficiency gains of up to 60% at the server side and 90% at the client side. We also deployed our implementation of FlexDPDP (dynamic provable data possession (DPDP) with FlexList instead of RBaSL) on PlanetLab, demonstrating that FlexDPDP performs comparable to the most efficient static storage scheme (provable data possession (PDP)) while providing dynamic data support.Publication Metadata only Design of curved composite panels for optimal dynamic response using lamination parameters(Elsevier Sci Ltd, 2018) N/A; Department of Mechanical Engineering; Serhat, Gökhan; Başdoğan, İpek; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 179940In this paper, dynamic response of composite panels is investigated using lamination parameters as design variables. Finite element analyses are performed to observe the individual and combined effects of different panel aspect ratios, curvatures and boundary conditions on the dynamic responses. Fundamental frequency contours for curved panels are obtained in lamination parameters domain and optimal points yielding maximum values are found. Subsequently, forced dynamic analyses are carried out to calculate equivalent radiated power (ERP) for the panels under harmonic pressure excitation. ERP contours at the maximum fundamental frequency are presented. Optimal lamination parameters providing minimum ERP are determined for different excitation frequencies and their effective frequency bands are shown. The relationship between the designs optimized for maximum fundamental frequency and minimum ERP responses is investigated to study the effectiveness of the frequency maximization technique. The results demonstrate the potential of using lamination parameters technique in the design of curved composite panels for optimal dynamic response and provide valuable insight on the effect of various design parameters.Publication Metadata only Femtosecond laser ablation assisted nfc antenna fabrication for smart contact lenses(Wiley, 2022) N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; N/A; N/A; N/A; N/A; Department of Mechanical Engineering; Mirzajani, Hadi; İstif, Emin; Abbasiasl, Taher; Mirlou, Fariborz; Özkahraman, Ecem Ezgi; Hasanreisoğlu, Murat; Beker, Levent; Researcher; Other; PhD Student; PhD Student; N/A; Faculty Member; Faculty Member; Department of Mechanical Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); n2STAR-Koç University Nanofabrication and Nanocharacterization Center for Scientifc and Technological Advanced Research; College of Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; N/A; School of Medicine; College of Engineering; N/A; N/A; N/A; N/A; N/A; 182001; 308798Smart contact lenses (SCLs) have drawn substantial interest for continuous health monitoring applications. Even though most of the reported works utilize near-field communication (NFC) or inductive coupling for wireless powering and data transmission, developing a scalable and rapid fabrication technique for annular ring antennas confined in a small contact lens area is still an unsolved challenge. Here, femtosecond laser ablation is employed for the first time as a simple, single-step, and highly precise fabrication technique for NFC antennas using conventional flexible printed circuit board materials. Antenna lines with depth and width of 9 and 35 mu m are achieved, respectively. The antenna with a footprint of 19.5 mm(2) is characterized in biological solution followed by aging, and bending tests, and a frequency deviation of less than %1 is recorded. A real-life application is demonstrated by fabricating an SCL embedded with the antenna, an NFC chip, and an electrochemical sensor for wireless monitoring of glucose in artificial tear solution by a smartphone. The device could successfully quantify biologically relevant glucose concentrations ranging from 0.2 to 1 mM with a limit-of-detection of 66 mu M. In addition, device response to interfering molecules is less than +/- 1 nA, and the spike-and-recovery test is successfully demonstrated.Publication Metadata only Automatic detection of road types from the third military mapping survey of Austria-Hungary historical map series with deep convolutional neural networks(IEEE-inst Electrical Electronics Engineers inc, 2021) N/A; N/A; Department of History; Can, Yekta Said; Gerrits, Petrus Johannes; Kabadayı, Mustafa Erdem; Resercher; Master Student; Faculty Member; Department of History; College of Social Sciences and Humanities; Graduate School of Social Sciences and Humanities; College of Social Sciences and Humanities; N/A; N/A; 33267With the increased amount of digitized historical documents, information extraction from them gains pace. Historical maps contain valuable information about historical, geographical and economic aspects of an era. Retrieving information from historical maps is more challenging than processing modern maps due to lower image quality, degradation of documents and the massive amount of non-annotated digital map archives. Convolutional Neural Networks (CNN) solved many image processing challenges with great success, but they require a vast amount of annotated data. for historical maps, this means an unprecedented scale of manual data entry and annotation. in this study, we first manually annotated the Third Military Mapping Survey of austria-Hungary historical map series conducted between 1884 and 1918 and made them publicly accessible. We recognized different road types and their pixel-wise positions automatically by using a CNN architecture and achieved promising results.